Floatation separators

ABSTRACT

A floatation separator comprises a floatation tank containing a plurality of vertically spaced apart parallel inclined plates for defining a plurality of parallel inclined chambers in which impurities are separated from the water to be treated by floatation. Each inclined chamber is provided with an inlet port for the water to be treated near its upper end and a discharge port for the treated water near the lower end thereof intermediate the upper and lower inclined plates of a chamber.

United States Patent Horiguchi et al.

FLOATATION SEPARATORS Inventors: Tadao Horlguchi; Katsuml Tagomori, bothof Yokohama, Japan Assignee:

Kurita Water Industries, Ltd.,

l-lodogaya-ku, Yokohama-shi, Japan Filed:

Sept. 14, 1971 Appl. No.: 180,429

Foreign Application Priority Data Nov. 17, 1970 Japan 45/101237 Sept.28, 1970 Japan 45/84797 Nov. 12, 1970 Japan 45/99670 Nov. 13, 1970Japan". 45/99951 Nov. 14, 1970 Japan.... 45/100333 Nov. 17, 1970 Japan45/101234 US. Cl 210/221, 210/521, 209/170,

261/77 Int. Cl. B03c 5/02 Field of Search. .[210/44, 83, 196,

[ 1 Aug. 28, 1973 References Cited UNITED STATES PATENTS Examiner-SamihN. Zaharna Assistant Examiner-Robert H. Spitzer Attorney-Flynn &Frishauf [5 7] ABSTRACT A floatation separator comprises a floatationtank containing a plurality of vertically spaced apart parallel inclinedplates for defining a plurality of parallel inclined chambers in whichimpurities are separated from the water to be treated by floatation.Each inclined chamber is provided with an inlet port for the water to betreated near its upper end and a discharge port for the treated waternear the lower end thereof intermediate the upper and lower inclinedplates of a chamber.

15 Claims, 7 Drawing Figures Patented Aug. 28, 1973 5 Sheets-Sheet IPatented Aug. 28, 1973 3,754,656

5 Sheets-Sheet 2 Pafented Aug. 28, 1973 5 Sheets-Sheet 4 Patented Aug.28, 1973 5 Sheets-Sheet 5 FLOATATION SEPARATORS BACKGROUND OF THEINVENTION This invention relates to a floatation separator and moreparticularly to apparatus for removing impurities contained in water byfloatation separation to obtain clear water.

The capability or efficiency of such a floatation separator isdetermined by treatment capacity which is shown by the quantity of watertreated per unit area per unit time. In a floatation separator in orderto increase the treatment capacity it is essential to decrease as far aspossible the turbulent flow of the water in the floatation chambercaused by the water being treated which is admitted into the chamber andby the flow of water discharged from the chamber. It is also necessaryto decrease the turbulent flow or downward flow in the floatationchamber caused by the rising water accompanying floatation of airbubbles or flocks.

Even when such factors that interfere with ideal floatation separationare completely eliminated, the treatment capacity is limited because ofthe limitation of the inherent floating speed of the flocks. Increase ofthe treating speed per unit area occupied by the apparatus beyond thislimit is made possible by the provision of inclined plates in theapparatus for increasing the floatation area and such apparatus iscalled an inclined plate type floatation apparatus. With this type ofthe floatation apparatus the theoretical treating speed per unit areaoccupied can be thought to increase with the number of flow passagespartitioned by the inclined plates. Actually however, in an apparatusprovided with about inclined plates the efficiency is only several timeshigher than the conventional apparatus not equipped with inclinedplates. This is because installation of the inclined plates introducesnew problems for the floatation separator. One major problem involvesthe difficulty in the uniform distribution of the water being treatedamong respective flow passages defined by the inclinedplates. In a flowpassage which receives a large quantity of the water, the water mayreach the exit end of the passage before the solids completely floatorthe perfect floatation may be prevented by the turbulent flow in thepassage for which reason it is obliged to limit the quantity of waterintroducedinto the apparatus. Where the water being treated is admittedat a portion close to the discharge port of the treated water, that'isthe lower portion of the floatation chamber, there is an advantage thatthe retention time in the flow passages is prolonged. However, owing tothe close installation of the inlet port and the discharge port, thewater being treated has a tendency to flow directly to the dischargeport. Furthermore, the floating flocks move over a wide area of thefloatation chamber, so that the water therein is circulated through thechamber by this movement to flow into respective flow passages, thusrendering it difficult to control the flow of respective liquid phases.For this reason, although three phases, viz. the water being treatedcontaining floatable matters, the water which has been treated and thefroths containing the floatable matters are well separated in respectiveflow passages, they will flow into the upper and lower stages of theflow passages when these phases flow out of the passages, with theresult that they are mixed again with another effluent phase, thusdecreasing the efficiency of separation of the apparatus. 1

SUMMARY OF THE INVENTION It is an object of this invention to provide anew and improved floatation separator which can perform the desiredfloatation separation without the accompanying difficulties describedabove.

Another object of this invention is to provide an improved floatationseparator including a plurality of parallel inclined floatation chambersin which an inlet port for the water being treated, a discharge port forthe treated water and a discharge port for the froths are provided ineach inclined chamber such that the froths separated from the water byfloatation can flow freely toward the froth discharge port without beingentrained in the flow of the water.

A further object of this invention is to provide an improved floatationseparator of the multi-stage type in which the froths separated in thelower stages are prevented from flowing into upper stages. This can beaccomplished by providing an independnet froth floating passage for eachinclined floatation chamber.

Yet another object of this invention is to provide an improvedcoagulation separator in which the contaminants or impurities containedin the water to be treated are coagulated to form flocks before thewater is admitted into the floatation separator for improving theefficiency of separation by floatation.

A still further object of this invention is to improve the efficiency ofseparation of the flocks by injecting fine air bubbles thus causing theflocks to collect on the air bubbles.

In accordance with this invention, there is provided a floatationseparator comprising a floatation tank, a plurality of vertically spacedapart parallel inclined plates mounted in the tank for definingaplurality of parallel inclined chambers, an inlet port for the water tobe treated which is positioned near the upper end of each inclinedchamber close to the upper inclined plate defining the same, a dischargeport for the froths which is provided at the upper end of each inclinedchamber, and a discharge port for the treated water at the lower end ofeach inclined chamber.

A substantially vertical guide plate portion extends from the upper endof each of the inclined plates. Where respective vertical guide platesare aligned vertically, a single common froths floating or risingpassage is formed whereas where these vertical guide plates are placedin the horizontal direction, a plurality of independent froth floatingpassages are formed between the froth discharge ports of respectiveinclined chambers and the upper portion of the floatation tank where thefroths are condensed and removed, Alternatively, such froth floatingpassages may be provided outside the floatation tank. In any case, thefroths from the inclined chambers at lower stages are positivelyprevented from entering the inclined chambers at higher stages. Thus,the phases of the froths and of water which are separated by floatationin respective inclined chambers are clearly separated so that theefficiency of separation of the froths by floatation can be greatlyimproved.

In accordance with another feature of the invention, there is provided acoagulation tank between the main pipe which feeds the water to betreated and the. respective inclined passages and a coagulating agent isadmitted into the coagulation tank to convert the contaminants orimpurities in the water into flocks. Fine air bubbles are also blowninto the inclined passages to collect thereon the flocks thus promotingtheir buoyancy.

Additionally, pressurized water containing gas or air dissolved thereinis also prepared and admitted into respective inclined chambers togetherwith the water to be treated. The gas or air bubbles liberated from thispressurized water are also effective to promote the separation of thefroths by floatation.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows a vertical section of oneembodiment of the floatation separator embodying the invention;

FIG. 2 shows a vertical section similar to FIG. 1 showing a modifiedembodiment of the invention;

FIGS. 3 and 4 show vertical sections similar to FIG. 1 showing stillanother embodiment of the invention;

FIG. 5 shows a vertical section of another embodiment in which rinsingwater tubes and air diffuser tubes are provided in inclined chambers;

FIG. 6 is a diagram to show the connection between a coagulation tankand a distribution tank associated with the floatation tank; and

FIG. 7 is a diagram showing the detail of the air supply pipe connectedto the inlet pipe for the water to be treated.

Throughout the drawings like or corresponding portions or elements aredesignated by the same reference numerals.

DESCRIPTION OF THE PREFERRED EMBODIMENTS With reference first to FIG.v Iof the accompanying drawing, the embodiment of the floatation separatorshown therein comprises a floatation tank 1 containing a plurality ofinclined chambers 3 defined by a plurality of vertically aligned spacedapart parallel inclined plates 2, inlet ports 4 for the water to betreated which are provided at the upper portion of the respectiveinclined chambers 3 close to the upper inclined plates 2, dischargeports 5 at the top of respective inclined chambers 3 for dischargingseparated froths, and discharge ports 6 at the lower end of the inclinedchambers for discharging the treated water. The floatation tank 1preferably has a square or rectangular crosssection of the sizedetermined depending upon the quantity of the water to be treated. Theinclined plates 2 are disposed parallel with each other so that thevertical spacing therebetween is substantially uniform. An angle ofinclination of the order of 45 is generally preferred but the best angleis selected for a given floatable substance. I

At the upper end of each inclined plate 2 is a vertical guide plate 7 todefine froth floating passages 8 above the discharge ports 5 for thefroths. The lower portion of each inclined chamber 3 is completelyclosed except for a sludge discharge port 9 leading to a common sludgedrain pipe 10. Discharge ports 6 for the treated water are communicatedwith a pipe 11 for the treated water. The upper end of each frothfloating passage 8 is communicated with a concentrating chamber 12 withits upper level opened to the atmosphere and a froth discharge port 13is opened near the liquid level of the concentrating chamber. Althoughthe inlet ports 4 for the water to be treated are shown to direct thewater to flow in parallel with inclined plates 2 they may be openedtowards the discharge ports 5 for froths or opened toward the upperpart. In any case, it is advantageous to create flow of water to assistthe floating of the froths. Each discharge port 6 for the treated wateris shown to open at an intermediate point between ad- 5 jacent inclinedplates.

' 3 through inlet ports 4. The resulting flocks existing in the water tobe treated adhere to air bubbles to form froths. The froths floatupwardly through discharge ports 5 and via froth floating passages 8into concentrating chamber 12 in which they are concentrated anddischarged out of the tank through discharge port 13. The water fromwhich the froths have been separated in the manner as above describeddescends at a low speed and flows out into pipe 11 as clean treatedwater via discharge ports 6. At portions in each inclined chamber 3,beneath inlet port 4, some of the froths accompanied by the descendingwater tend to float upwardly and some of the sludges tend toprecipitate, but there is formed no turbulent flow and circulation ofthe water. In other words, the water flows uniformly towards the bottom,thus producing clean treated water. Most of the froths float upwardly tobe discharged but only a small portion thereof precipitates to bedischarged through sludge discharge port 9 and pipe 10. The purpose ofvertical guide plates 7 is to isolate respective froth floating passages8 to prevent the froths in the inclined chambers at lower stages fromflowing into inclined chambers at higher stages, thus increasing theefficiency of separation. With the illustrated apparatus, since thewater to be treated flows upwardly along inclined plates at relativelyhigh levels in a plurality of independent inclined chambers defined bythe inclined plates and since the distance of movement of the froths isrelatively short, the quantity of the water that is caused to move bythe floating movement of the froths is relatively small so that nocirculation of the water in the inclined chambers will result.Consequently, the froths float up efficiently because there is notendency of the froths to flow downwardly together with the downwardlymoving water. Thus, most of the froths contained in the water to betreated which has been admitted into the inclined chambers through inletport 4 is accumulated at the upper portions of the inclined plates in arelatively short time. The water containing remaining froths graduallymoves toward the discharge port 6 during which froths having smallersize and smaller buoyancy complete floatation to produce clean waterwhich is discharged through discharge ports 6. Since the spacing betweenadjacent inclined plates 2 is small as in the conventional design, thefroths can readily reach the lower surfaces of the upper inclined platesand are separated from the flow of water thus decreasing the floatingtime. Accordingly the capacity of the apparatus is improvedcorrespondingly.

The froths that have reached the lower surface of the upper inclinedplate of each inclined chamber then move upwardly along the inclinedsurface to gather at the uppermost portion of the inclined chamber.There-' after, the froths float upwardly into the concentrating chamber.12 at the upper portion of the apparatus through froth floating passages8.

As above described, since in the novel floatation sep arator, the inletport for the water to be treated, the discharge port for the treatedwater and the discharge port for the froths are provided in each of theinclined chambers defined by the inclined plates, in such positions anddirections that does not cause any turbulent flow, various phasesseparated in respective inclined chambers flow independently without thefear of being mixed again. For this reason, the treating ability of eachinclined floatation chamber is greatly improved when compared with theprior art floatation separation apparatus.

Moreover, since the number of vertically stacked stages of thefloatation chambers can be increased with the quantity of water to betreated, it is possible to increase the capacity of the apparatus perunit floor area thereof by a factor of or more when compared with thatof the prior art apparatus. To demonstrate this, one example of theresult of experiments is shown hereinbelow. With regard to a singleinclined chamber, where the inlet port for the water being treated waspositioned, at the upper portion of the chamber, the treatment capacity(the quantity of water treated per unit area occupied by the apparatus)was found to be l3.0 m/hr, and the percentage of removal of the solidswas 98 percent. These data should be compared with the treatmentcapacity of 2.7 m/hr and the percentage of removal of the solids of 94percent which were obtained when the inlet port was positioned at thelower portion. Where three stages of the inclined floatation chamberswere used but where guide plates 7 were omitted, a treatment capacity of40.6 m/hr and the percentage of removal of 98 percent were obtainedwhereas with the illustrated apparatus these data were improved to 51.5m/hr and 98 percent, respectively, showing a substantial improvement inthe treating efficiency.

The modification shown in FIG. 2 is substantially identical to thatshown in FIG. 1 except for a different arrangement of the guide plates14 and the froth floating passages 15. More particularly, instead ofutilizing guide plates of different height, the upper ends of .all guideplates 14 terminate at the same level in the concentrating chamber 12 soas to completely isolate respective froth floating passages 15. Ahorizontal skimmer 16 is provided near the upper level in the floatationtank 1 to discharge collected froths through a discharge port 17 for thefroths. With this construction, it is possible to completely prevent thefroths from the lower stages from flowing into the inclined chambers 3at the upper stages. Thus, the froths in respective chambers can freelyfloat up without being influenced by the downward flow of the waterwhereby the efficiency of separation can be improved.

It should be understood that the arrangement of the guide plates and thefroth floating passages can be modified in various ways. FIGS. 3 and 4illustrate other arrangements. In the embodiment shown in FIG. 3, guideplates 19 are provided on the outside of tank 1 at the upper portionthereof to guide froths separated in respective inclined chambers 3 tothe upper portion of the tank 1 through openings 18 at the side thereofand a plurality of substantially vertical froth floating passages 19.With this modification, it is possible to equalize the length of allinclined chambers 3 thus as suring equal efficiency of separation in allchambers.

In the modified embodiment shown in FIG. 4, a curved guide plate 21 isformed at the upper end of each inclined plate 2 and the upper end ofeach guide plate 21 is terminated close to the lower surface of thecurved guide plate positioned thereabove to form a narrow exit port 22for the separated froths. The vertical portions of respective guideplates are aligned in the vertical direction to form a common frothfloating passage 23 of uniform cross-section between these verticalportions and one side wall of tank 1. This embodiment is advantageous inthat it is possible to form a plurality of inclined floatation chambers3 of the same size and same length by using the inclined plates andguide plates of the same size and of the same configuration. Byconnecting the inclined chambers to the common froth floating passagethrough narrow exit port 22 it is possible to completely prevent thefroths from the lower stages from flowing into the inclined chambers athigher stages. Moreover, the froths can rise freely without beinginfluenced by the downward flow of the water. In the embodiments shownin FIGS. 1 and 2, wherein independent froth floating passages areprovided for different inclined chambers, the inclined chambers havedifferent lengths. More particularly, the upper chambers have shorterlengths with the result that their efficiency of separation decreasestoward the upper part. In contrast, with the construction shown in FIG.4, the length of all inclined chambers is made equal by the provision ofa common vertical froth floating passage 23, thus equalizing andimproving the efficiency of separation in respective chambers.

The modification shown in FIG. 5 is substantially identical to thatshown in FIG. 4 except that rinsing water pipes 24 positioned close tothe lower inclined plates near the upper ends of the inclined chambers 3for ejecting rinsing water toward the lower part. Further, at the lowerend of each chamber, an air diffuser 25 is positioned near the upperinclined plate to eject air bubbles toward the upper part. As theseparation by floatation is continued, a portion of the precipitatedsludge or floated froth will come to deposit on the upper or lowersurface of the inclined plates and such deposited sludge or froths peeloff from time to time to be entrained in the flow of the water beingtreated. In this embodiment, however, since there are provided rinsingwater pipes 24 at the upper ends of the inclined chambers 3 and airdiffuser 25 at the lower ends thereof it is possible to clean theinclined chambers. To this end, after the admission of the water to betreated into the inclined chambers has been interrupted air underpressure is ejected through air diffuser 25 to remove the frothsdeposited on the lower surfaces of the inclined plates 2. Thereafter,rinsing water is ejected through rinsing water pipes 24 to drain thesludge through discharge port 9 and drain pipe 10. By performingintermittently this cleaning operation, it is possible to stabilize theoperation of the apparatus.

Turning now to FIGS. 6 and 7, there is shown an improved control systemsuitable for use in combination with any one of the embodiments shown inFIGS. 1 to 5. More specifically, there are provided means for causingthe water to be treated and admitted into tank 1 through inlet pipes 4to undergo a coagulation reaction for converting all contaminants intofloatable flocks and means for concurrently admitting pressurized watercontaining gas or air dissolved therein to form fine gas bubbles whichare effective to collect the flocks, thus improving the efficiency ofremoval. In FIGS. 6 and 7, the construction of the floatation tank 1 perse is identical to that already described in connection with FIGS. 1 5.

In the embodiment shown in FIG. 6, there are provided a main pipe 26 forfeeding the water to be treated, a chemical injection tube 28 connectedthereto and a coagulation tank 27 connected to main pipe 26 via acoagulation mixer having a tortuous passage. The coagulation tank 27comprises an outer cylinder 29, an

inner cylinder 30 having a closed upper end and a water inlet pipe 300extending vertically to the closed upper end of the inner cylinder 30.The lower end of the inner cylinder is spaced apart from the bottom ofthe outer cylinder to define a flow passage and an exit port 31 isformed at the top of the outer cylinder. It should be understood thatthe construction and arrangement of coagulation tank 27, chemicalinjection pipe 28 and coagulation mixer 32 are not limited to theparticular ones illustrated in the drawing and that any one of wellknown coagulation tanks can also be used provided that the impuritiescan react with the coagulation agent added into the water being treated.It is also to be understood that the coagulation tank may contain achemical injection means and a mixer.

The exit port 31 of the coagulation tank 27 is connected to adistributor tank 33 which comprises an inlet chamber not shown and adistributing chamber 34 of the same number as the inclined chambers 3 inthe floatation tank 1. The inlet chamber and the distributing chambers34 are communicated with each other by means of a partition wallprovided with a plurality of V shaped notches. When the distributor tank33 is mounted at a higher level than the floatation tank 1, it ispossible to supply the water to be treated to the floatation tank byutilizing the difference in liquid heads. However, the distributor tankmay be located at a lower level in which case a suitable pump is used.Distributing chambers 34 of the distributor tank 33 are connected tocorresponding inclined chambers 3 through inlet pipes 37, respectively,which are connected to a gas supply pipe 38. The opposite end of gassupply pipe 38 is connected to a gas mixing or dissolving device (seeFIG. 7to be described later) for admitting into the inclined chamberspressurized water containing gas mixed or dissolved therein.

In operation, a suitable coagulation agent is added into the water to betreated such as sewerage, waste water or sludge through chemicalinjection pipe 28. The mixture is uniformly agitated and mixed while itpasses through the coagulation mixer 32 and thence admitted into thecoagulation tank 27. While the mixture flows downwardly and thenupwardly through the coagulation tank the coagulation agent will reactwith the impurities contained in the water thus converting them intofloatable flocks. The water containing the resulting flocks is admittedinto respective inclined chambers 3 via distributor tank 33 and inletpipes 37. The pressurized water containing dissolved gas is introducedinto respective inlet pipes 37 so that the mixture of the water beingtreated and the pressurized water is uniformly admitted into respectiveinclined chambers 3. Under these conditions, the interior of thefloatation tank I is maintained at the atmospheric pressure, so that thepressure of the pressurized water is relieved to form fine gas or airbubbles. Consequently, the flocks adhere to the air bubbles to formfloatable froths. These froths float upwardly through froth floatingpassage 23, concentrated in the concentrating chamber 12 and are finallydischarged outwardly through discharge port 17 by the action of skimmer16, as has been described above.

In this embodiment, although the inlet ports 4 for the water beingtreated are closely positioned in the floatation tank 1 with respect tothe froth discharge ports 22, since the coagulation agent is added tothe water and thecoagulation reaction occurs in the coagulation tank 27before the water is admitted into the floatation tank, there is no fearthat unreacted impurities are introduced into the floatation tank butinstead they are converted into flocks so that it is possible to improvethe operating efficiency of the floatation tank. Moreover, as the waterthat has already undergone the coagulation reaction is distributeduniformly among respective inclined chambers through the action of thedistributor tank 33 each inclined chamber can operate at its optimumefficiency.

In this embodiment, since the coagulation tank 27 takes the form of acylindrical tank and since the distributor tank 33 is located above tank27, addition thereof to the multi-stage type floatation tank does notresult in any substantial increase in the space of installation, therebyproviding a compact unit using a small amount of floor space.

The embodiment shown in FIG. 7 is substantially identical to that shownin FIG. 6 except that the other end of the pipe 38 for supplyingpressurized water containing air or gas dissolved therein is connectedto a gas separating tank 39.

The pressurized water containing dissolved gas is prepared by meansincluding an ejector 40, a pipe 41 for feeding water to the ejector 40,a gas supply pipe 42 communicated with the negative pressure portion ofthe ejector, a vertical tube 43 for extracting the mixture of the gasand water from the ejectorand the gas separating tank 39 connected tothe opposite end of the vertical tube 43. The opposite end of feed waterpipe 41 is connected to pipe 11 for the treated water to utilize aportion thereof. However, the feed water pipe 41 may be connected toanother source of water, for example to the main pipe 26. The verticalpipe 43 connected to the output of ejector 40 may take the form of ahair pin. Preferably, the length of pipe 43 should be more than 4 metersbecause the gas should be completely dissolved in the water while itpasses through pipe 43. The opposite end of this pipe is connected togas separating tank 39 and it is preferable to connect horizontally theend of pipe 43 as at 44 for separating surplus gas from water thusdecreasing the retention time of the gas in tank 39. The upper end ofgas separating tank 39 is connected to the negative pressure side ofejector 40 through a gas return pipe 45. The bottom of gas separationtank 39 is connected to respective pipes 37 for admitting the water tobe treated via pipe 38.

In operation, the water supplied through main pipe 26 is admitted intorespective inclined chambers 3 in the manner already described inconnection with FIG. 6. A portion of the treated water is supplied frompipe 11 to ejector 40 via pump 46 and pipe 41 to mix the water with thegas or air supplied through pipe 42 under pressure. The gas or air isdissolved in the water while it passes through vertical pipe 43. Surplusgas is separated from the water in gas separating tank 39 and thenreturned to ejector 40 to be used again. The pressurized watercontaining gas or air dissolved therein is supplied to inlet pipes 37through pipe 38 so as to be mixed with the water to be treated. Themixture is then admitted into respective inclined chambers 3 throughinlet ports 4.

In the gas dissolving device described above, since gas is dissolved inwater in the vertical tube connected to the output of the ejector, thegas is dissolved at a higher efficiency than the conventional gasdissolving system. Moreover, since the gas separating tank is requiredto separate only surplus gas it is possible to reduce the size of thetank, thus reducing the floor space requirement of the entire apparatus.

While the invention has been described in terms of some preferredembodiments thereof it should be understood that many changes andmodifications will be obvious to one skilled in the art withoutdeparting from the true spirit and scope of the invention as defined inthe appended claims.

We claim:

1. A floatation separator comprising:

a floatation tank;

a plurality of vertically spaced apart substantially parallel inclinedplates mounted in said tank for defining a plurality of substantiallyparallel inclined chambers;

an inlet port for the water to be treated, said inlet port beingpositioned near the upper end of each inclined chamber close to theupper inclined plate defining each inclined chamber;

a plurality of upwardly extending guide plates extending from the upperends of said inclined plates respectively, said guide plates extendingupwardly at a steeper angle than said inclined plates, said guide platesdefining a discharge port for the froths at the upper end of eachinclined chamber, and definining at least one froth floating passageextending between said froth discharge ports and the upper portion ofsaid floatation tank; and discharge port for the treated water at thelower end of each inclined chamber, said treated water discharge portbeing located intermediate the adjacent upper and lower inclined plateswhich define a chamber.

2. The floatation separator according to claim 1 comprising a pluralityof sludge discharge ports at the lower end of respective inclinedchambers, said sludge discharge ports being below the respective treatedwater discharge ports.

3. The floatation separator according to claim 2 wherein saidsludgedischarge ports are located adjacent the inclined plates defining thefloors of respective inclined chambers.

4. The floatation separator according to claim 1 wherein a plurality ofindependent froth floating passages are formed outside said floatationtank to connect said froth discharge ports to the upper portion of saidfloatation tank.

5. The floatation separator according to claim 1 wherein said guideplates are curved and have substantially vertical portions, the verticalportions of said curved guide plates being aligned substantiallyvertically to define a common froth floating passage, the upper ends ofsaid guide plates terminating close to adjacent ones of said inclinedplates to define said froth discharge ports therebetween.

6. The floatation separator according to claim 5 wherein said inclinedand guide plates are all substantially identical in size and shape.

7. The floatation separator according, to claim 1 wherein a pipe foradmitting rinsing water is provided at the upper portion of eachinclined chamber and an air diffuser is provided at the lower portion ofeach inclined chamber.

8. The floatation separator according to claim 1 which further comprisesa main pipe for feeding the water to be treated, a coagulation tankconnected to said main pipe, means for supplying a coagulation agent forsaid coagulation tank, a distributor tank connected between saidcoagulation tank and said inlet ports and means for supplying to saidinlet ports pressurized water containing gas or air dissolved therein.

9. The floatation separator according to claim 8 wherein saidcoagulation tank comprises an outer cylinder and an inner cylinderhaving a closed upper end, and a pipe connected to said main pipe andextending near the closed upper end of said inner cylinder.

10. The floatation separator according to claim 8 wherein saidpressurized water supply means includes a device for dissolving gas orair in pressurized water.

11. The floatation separator according to claim 10 wherein said devicecomprises an ejector for admixing water and gas, means for supplyingpressurized water to said ejector, means for supplying said gas to thenegative pressure side of said ejector, a vertical output tube forreceiving the mixture of said water and said gas from said ejector, agas separating tank connected to the opposite end of said vertical pipe,and means for returning the gas separated in said gas separating tankback, to said ejector.

12. The floatation separator according to claim 11, wherein saidvertical outlet pipe takes the form of a hair pin and said verticaloutlet pipe is terminated with a horizontal section at said opposite endconnected to said gas separating tank.

13. The floatation separator according to claim 1 wherein said inclinedplates are inclined at an angle of about 45.

14. The floatation separator according to claim 1 wherein said tank issquare or rectangular in crosssection.

15. The floatation separator according to claim 1 wherein said guideplates are connected to their respective inclined plates.

1. A floatation separator comprising: a floatation tank; a plurality ofvertically spaced apart substantially parallel inclined plates mountedin said tank for defining a plurality of substantially parallel inclinedchambers; an inlet port for the water to be treated, said inlet portbeing positioned near the upper end of each inclined chamber close tothe upper inclined plate defining each inclined chamber; a plurality ofupwardly extending guide plates extending from the upper ends of saidinclined plates respectively, said guide plates extending upwardly at asteeper angle than said inclined plates, said guide plates defining adischarge port for the froths at the upper end of each inclined chamber,and definining at least one froth floating passage extending betweensaid froth discharge ports and the upper portion of said floatationtank; and a discharge port for the treated water at the lower end ofeach inclined chamber, said treated water discharge port being locatedintermediate the adjacent upper and lower inclined plates which define achamber.
 2. The floatation separator according to claim 1 comprising aplurality of sludge discharge ports at the lower end of respectiveinclined chambers, said sludge discharge ports being below therespective treated water discharge ports.
 3. The floatation separatoraccording to claim 2 wherein said sludge discharge ports are locatedadjacent the inclined plates defining the floors of respective inclinedchambers.
 4. The floatation separator according to claim 1 wherein aplurality of independent froth floating passages are formed outside saidfloatation tank to connect said froth discharge ports to the upperportion of said floatation tank.
 5. The floatation separator accordingto claim 1 wherein said guide plates are curved and have substantiallyvertical portions, the vertical porTions of said curved guide platesbeing aligned substantially vertically to define a common froth floatingpassage, the upper ends of said guide plates terminating close toadjacent ones of said inclined plates to define said froth dischargeports therebetween.
 6. The floatation separator according to claim 5wherein said inclined and guide plates are all substantially identicalin size and shape.
 7. The floatation separator according to claim 1wherein a pipe for admitting rinsing water is provided at the upperportion of each inclined chamber and an air diffuser is provided at thelower portion of each inclined chamber.
 8. The floatation separatoraccording to claim 1 which further comprises a main pipe for feeding thewater to be treated, a coagulation tank connected to said main pipe,means for supplying a coagulation agent for said coagulation tank, adistributor tank connected between said coagulation tank and said inletports and means for supplying to said inlet ports pressurized watercontaining gas or air dissolved therein.
 9. The floatation separatoraccording to claim 8 wherein said coagulation tank comprises an outercylinder and an inner cylinder having a closed upper end, and a pipeconnected to said main pipe and extending near the closed upper end ofsaid inner cylinder.
 10. The floatation separator according to claim 8wherein said pressurized water supply means includes a device fordissolving gas or air in pressurized water.
 11. The floatation separatoraccording to claim 10 wherein said device comprises an ejector foradmixing water and gas, means for supplying pressurized water to saidejector, means for supplying said gas to the negative pressure side ofsaid ejector, a vertical output tube for receiving the mixture of saidwater and said gas from said ejector, a gas separating tank connected tothe opposite end of said vertical pipe, and means for returning the gasseparated in said gas separating tank back to said ejector.
 12. Thefloatation separator according to claim 11, wherein said vertical outletpipe takes the form of a hair pin and said vertical outlet pipe isterminated with a horizontal section at said opposite end connected tosaid gas separating tank.
 13. The floatation separator according toclaim 1 wherein said inclined plates are inclined at an angle of about45*.
 14. The floatation separator according to claim 1 wherein said tankis square or rectangular in cross-section.
 15. The floatation separatoraccording to claim 1 wherein said guide plates are connected to theirrespective inclined plates.